Documented functions and controls in expression language.

Better error checking in operator calls.

git-svn-id: http://google-refine.googlecode.com/svn/trunk@127 7d457c2a-affb-35e4-300a-418c747d4874

src/main/java/com/metaweb/gridworks/commands/util/GetExpressionLanguageInfoCommand.java

@@ -1,6 +1,7 @@
 package com.metaweb.gridworks.commands.util;
 
 import java.io.IOException;
+import java.util.Properties;
 import java.util.Map.Entry;
 
 import javax.servlet.ServletException;
@@ -22,6 +23,8 @@ public class GetExpressionLanguageInfoCommand extends Command {
 		
 		try {
 			JSONWriter writer = new JSONWriter(response.getWriter());
+			Properties options = new Properties();
+			
 			writer.object();
 			
 			writer.key("functions");
@@ -29,8 +32,7 @@ public class GetExpressionLanguageInfoCommand extends Command {
 			{
 			    for (Entry<String, Function> entry : Parser.functionTable.entrySet()) {
 			        writer.key(entry.getKey());
-			        writer.object();
-			        writer.endObject();
+			        entry.getValue().write(writer, options);
 			    }
 			}
 			writer.endObject();
@@ -40,8 +42,7 @@ public class GetExpressionLanguageInfoCommand extends Command {
             {
                 for (Entry<String, Control> entry : Parser.controlTable.entrySet()) {
                     writer.key(entry.getKey());
-                    writer.object();
-                    writer.endObject();
+			        entry.getValue().write(writer, options);
                 }
             }
             writer.endObject();

src/main/java/com/metaweb/gridworks/expr/Control.java

@@ -2,6 +2,8 @@ package com.metaweb.gridworks.expr;
 
 import java.util.Properties;
 
-public interface Control {
+import com.metaweb.gridworks.Jsonizable;
+
+public interface Control extends Jsonizable {
 	public Object call(Properties bindings, Evaluable[] args);
 }

src/main/java/com/metaweb/gridworks/expr/Function.java

@@ -2,6 +2,8 @@ package com.metaweb.gridworks.expr;
 
 import java.util.Properties;
 
-public interface Function {
+import com.metaweb.gridworks.Jsonizable;
+
+public interface Function extends Jsonizable {
 	public Object call(Properties bindings, Object[] args);
 }

src/main/java/com/metaweb/gridworks/expr/OperatorCallExpr.java

@@ -17,66 +17,40 @@ public class OperatorCallExpr implements Evaluable {
 			args[i] = _args[i].evaluate(bindings);
 		}
 		
+		if (args.length == 2) {
+			if (args[0] != null && args[1] != null) {
+                if (args[0] instanceof Number && args[1] instanceof Number) {
                 	if ("+".equals(_op)) {
-			if (args.length == 2) {
-				if (args[0] instanceof Number && args[1] instanceof Number) {
 						return ((Number) args[0]).doubleValue() + ((Number) args[1]).doubleValue();
-				} else {
-					return args[0].toString() + args[1].toString();
-				}
-			}
                 	} else if ("-".equals(_op)) {
-			if (args.length == 2) {
-				if (args[0] instanceof Number && args[1] instanceof Number) {
 						return ((Number) args[0]).doubleValue() - ((Number) args[1]).doubleValue();
-				}
-			}
                 	} else if ("*".equals(_op)) {
-			if (args.length == 2) {
-				if (args[0] instanceof Number && args[1] instanceof Number) {
 						return ((Number) args[0]).doubleValue() * ((Number) args[1]).doubleValue();
-				}
-			}
                 	} else if ("/".equals(_op)) {
-			if (args.length == 2) {
-				if (args[0] instanceof Number && args[1] instanceof Number) {
 						return ((Number) args[0]).doubleValue() / ((Number) args[1]).doubleValue();
-				}
-			}
                 	} else if (">".equals(_op)) {
-            if (args.length == 2) {
-                if (args[0] instanceof Number && args[1] instanceof Number) {
 	                    return ((Number) args[0]).doubleValue() > ((Number) args[1]).doubleValue();
-                }
-            }
                 	} else if (">=".equals(_op)) {
-            if (args.length == 2) {
-                if (args[0] instanceof Number && args[1] instanceof Number) {
 	                    return ((Number) args[0]).doubleValue() >= ((Number) args[1]).doubleValue();
-                }
-            }
                 	} else if ("<".equals(_op)) {
-            if (args.length == 2) {
-                if (args[0] instanceof Number && args[1] instanceof Number) {
 	                    return ((Number) args[0]).doubleValue() < ((Number) args[1]).doubleValue();
-                }
-            }
                 	} else if ("<=".equals(_op)) {
-            if (args.length == 2) {
-                if (args[0] instanceof Number && args[1] instanceof Number) {
 	                    return ((Number) args[0]).doubleValue() <= ((Number) args[1]).doubleValue();
 		            }
                 }
-        } else if ("==".equals(_op)) {
-            if (args.length == 2) {
+                
+    			if ("+".equals(_op)) {
+    				return args[0].toString() + args[1].toString();
+    			}
+			}
+			
+	        if ("==".equals(_op)) {
                 if (args[0] != null) {
                     return args[0].equals(args[1]);
                 } else {
                     return args[1] == null;
                 }
-            }
 	        } else if ("!=".equals(_op)) {
-            if (args.length == 2) {
                 if (args[0] != null) {
                     return !args[0].equals(args[1]);
                 } else {

src/main/java/com/metaweb/gridworks/expr/controls/ForEach.java

@@ -4,6 +4,9 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Control;
 import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.VariableExpr;
@@ -50,4 +53,15 @@ public class ForEach implements Control {
         return null;
     }
     
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value(
+			"Evaluates expression a to an array. Then for each array element, binds its value to variable name v, evaluates expression e, and pushes the result onto the result array."
+		);
+		writer.key("params"); writer.value("expression a, variable v, expression e");
+		writer.key("returns"); writer.value("array");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/controls/ForNonBlank.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.controls;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Control;
 import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.ExpressionUtils;
@@ -36,4 +39,16 @@ public class ForNonBlank implements Control {
         return null;
     }
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value(
+			"Evaluates expression o. If it is non-blank, binds its value to variable name v, evaluates expression eNonBlank and returns the result. " +
+			"Otherwise (if o evaluates to blank), evaluates expression eBlank and returns that result instead."
+		);
+		writer.key("params"); writer.value("expression o, variable v, expression eNonBlank, expression eBlank");
+		writer.key("returns"); writer.value("Depends on actual arguments");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/controls/If.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.controls;
 
  import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Control;
 import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.ExpressionUtils;
@@ -21,4 +24,16 @@ public class If implements Control {
         return null;
     }
     
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value(
+			"Evaluates expression o. If it is true, evaluates expression eTrue and returns the result. " +
+			"Otherwise, evaluates expression eFalse and returns that result instead."
+		);
+		writer.key("params"); writer.value("expression o, expression eTrue, expression eFalse");
+		writer.key("returns"); writer.value("Depends on actual arguments");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/controls/With.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.controls;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Control;
 import com.metaweb.gridworks.expr.Evaluable;
 import com.metaweb.gridworks.expr.VariableExpr;
@@ -33,4 +36,15 @@ public class With implements Control {
         return null;
     }
     
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value(
+			"Evaluates expression o and binds its value to variable name v. Then evaluates expression e and returns that result"
+		);
+		writer.key("params"); writer.value("expression o, variable v, expression eNonBlank, expression eBlank");
+		writer.key("returns"); writer.value("Depends on actual arguments");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/And.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class And implements Function {
@@ -14,4 +17,14 @@ public class And implements Function {
 		}
 		return true;
 	}
+	
+	public void write(JSONWriter writer, Properties options)
+			throws JSONException {
+		
+        writer.object();
+        writer.key("description"); writer.value("ANDs two boolean values");
+        writer.key("params"); writer.value("boolean a, boolean b");
+        writer.key("returns"); writer.value("boolean");
+        writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Ceil.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Ceil implements Function {
@@ -13,4 +16,13 @@ public class Ceil implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the ceiling of a number");
+		writer.key("params"); writer.value("number d");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/EndsWith.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class EndsWith implements Function {
@@ -17,4 +20,13 @@ public class EndsWith implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns whether s ends with sub");
+		writer.key("params"); writer.value("string s, string sub");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Floor.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Floor implements Function {
@@ -13,4 +16,14 @@ public class Floor implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the floor of a number");
+		writer.key("params"); writer.value("number d");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
+
 }

src/main/java/com/metaweb/gridworks/expr/functions/Get.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 import com.metaweb.gridworks.expr.HasFields;
 
@@ -75,4 +78,17 @@ public class Get implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value(
+			"If o has fields, returns the field named 'from' of o. " +
+			"If o is an array, returns o[from, to]. " +
+			"if o is a string, returns o.substring(from, to)"
+		);
+		writer.key("params"); writer.value("o, number or string from, optional number to");
+		writer.key("returns"); writer.value("Depends on actual arguments");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/IndexOf.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class IndexOf implements Function {
@@ -17,4 +20,13 @@ public class IndexOf implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the index of sub first ocurring in s");
+		writer.key("params"); writer.value("string s, string sub");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/IsBlank.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.ExpressionUtils;
 import com.metaweb.gridworks.expr.Function;
 
@@ -11,4 +14,13 @@ public class IsBlank implements Function {
 		return args.length == 0 || ExpressionUtils.isBlank(args[0]);
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns whether o is null or an empty string");
+		writer.key("params"); writer.value("o");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/IsNotBlank.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.ExpressionUtils;
 import com.metaweb.gridworks.expr.Function;
 
@@ -11,4 +14,13 @@ public class IsNotBlank implements Function {
 		return args.length > 0 && !ExpressionUtils.isBlank(args[0]);
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns whether o is not null and not an empty string");
+		writer.key("params"); writer.value("o");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/IsNotNull.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class IsNotNull implements Function {
@@ -10,4 +13,13 @@ public class IsNotNull implements Function {
 		return args.length > 0 && args[0] != null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns whether o is not null");
+		writer.key("params"); writer.value("o");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/IsNull.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class IsNull implements Function {
@@ -10,4 +13,13 @@ public class IsNull implements Function {
 		return args.length == 0 || args[0] == null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns whether o is null");
+		writer.key("params"); writer.value("o");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Join.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Join implements Function {
@@ -33,4 +36,13 @@ public class Join implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the string obtained by joining the array a with the separator sep");
+		writer.key("params"); writer.value("array a, string sep");
+		writer.key("returns"); writer.value("string");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/LastIndexOf.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class LastIndexOf implements Function {
@@ -17,4 +20,14 @@ public class LastIndexOf implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the index of sub last ocurring in s");
+		writer.key("params"); writer.value("string s, string sub");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
+
 }

src/main/java/com/metaweb/gridworks/expr/functions/Length.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Length implements Function {
@@ -23,4 +26,13 @@ public class Length implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the length of o");
+		writer.key("params"); writer.value("array or string o");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Ln.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Ln implements Function {
@@ -13,4 +16,13 @@ public class Ln implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the natural log of n");
+		writer.key("params"); writer.value("number n");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Log.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Log implements Function {
@@ -13,4 +16,13 @@ public class Log implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the base 10 log of n");
+		writer.key("params"); writer.value("number n");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Max.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Max implements Function {
@@ -15,4 +18,13 @@ public class Max implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the greater of two numbers");
+		writer.key("params"); writer.value("number a, number b");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Min.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Min implements Function {
@@ -15,4 +18,13 @@ public class Min implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the smaller of two numbers");
+		writer.key("params"); writer.value("number a, number b");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Mod.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Mod implements Function {
@@ -16,4 +19,13 @@ public class Mod implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns a modulus b");
+		writer.key("params"); writer.value("number a, number b");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Not.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Not implements Function {
@@ -17,4 +20,14 @@ public class Not implements Function {
 		return o == null ? false : (
 			(o instanceof Boolean) ? ((Boolean) o).booleanValue() : Boolean.parseBoolean(o.toString()));
 	}
+	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the opposite of b");
+		writer.key("params"); writer.value("boolean b");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Or.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Or implements Function {
@@ -14,4 +17,14 @@ public class Or implements Function {
 		}
 		return false;
 	}
+	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns a OR b");
+		writer.key("params"); writer.value("boolean a, boolean b");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Replace.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Replace implements Function {
@@ -19,4 +22,14 @@ public class Replace implements Function {
 		return null;
 	}
 
+	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the string obtained by replacing f with r in s");
+		writer.key("params"); writer.value("string s, string f, string r");
+		writer.key("returns"); writer.value("string");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Round.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Round implements Function {
@@ -13,4 +16,13 @@ public class Round implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns n rounded");
+		writer.key("params"); writer.value("number n");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Slice.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Slice implements Function {
@@ -59,4 +62,16 @@ public class Slice implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value(
+			"If o is an array, returns o[from, to]. " +
+			"if o is a string, returns o.substring(from, to)"
+		);
+		writer.key("params"); writer.value("o, number from, optional number to");
+		writer.key("returns"); writer.value("Depends on actual arguments");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/Split.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class Split implements Function {
@@ -17,4 +20,13 @@ public class Split implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns the array of strings obtained by splitting s with separator sep");
+		writer.key("params"); writer.value("string s, string sep");
+		writer.key("returns"); writer.value("array");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/StartsWith.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class StartsWith implements Function {
@@ -16,5 +19,13 @@ public class StartsWith implements Function {
 		}
 		return null;
 	}
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
 	
+		writer.object();
+		writer.key("description"); writer.value("Returns whether s starts with sub");
+		writer.key("params"); writer.value("string s, string sub");
+		writer.key("returns"); writer.value("boolean");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/ToLowercase.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class ToLowercase implements Function {
@@ -14,4 +17,13 @@ public class ToLowercase implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns s converted to lowercase");
+		writer.key("params"); writer.value("string s");
+		writer.key("returns"); writer.value("string");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/ToNumber.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class ToNumber implements Function {
@@ -13,4 +16,14 @@ public class ToNumber implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns o converted to a number");
+		writer.key("params"); writer.value("o");
+		writer.key("returns"); writer.value("number");
+		writer.endObject();
+	}
+
 }

src/main/java/com/metaweb/gridworks/expr/functions/ToString.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class ToString implements Function {
@@ -13,4 +16,14 @@ public class ToString implements Function {
 		return null;
 	}
 
+	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns o converted to a string");
+		writer.key("params"); writer.value("o");
+		writer.key("returns"); writer.value("string");
+		writer.endObject();
+	}
 }

src/main/java/com/metaweb/gridworks/expr/functions/ToTitlecase.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class ToTitlecase implements Function {
@@ -28,4 +31,14 @@ public class ToTitlecase implements Function {
 		return null;
 	}
 	
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns s converted to titlecase");
+		writer.key("params"); writer.value("string s");
+		writer.key("returns"); writer.value("string");
+		writer.endObject();
+	}
+
 }

src/main/java/com/metaweb/gridworks/expr/functions/ToUppercase.java

@@ -2,6 +2,9 @@ package com.metaweb.gridworks.expr.functions;
 
 import java.util.Properties;
 
+import org.json.JSONException;
+import org.json.JSONWriter;
+
 import com.metaweb.gridworks.expr.Function;
 
 public class ToUppercase implements Function {
@@ -14,4 +17,13 @@ public class ToUppercase implements Function {
 		return null;
 	}
 
+	public void write(JSONWriter writer, Properties options)
+		throws JSONException {
+	
+		writer.object();
+		writer.key("description"); writer.value("Returns s converted to uppercase");
+		writer.key("params"); writer.value("string s");
+		writer.key("returns"); writer.value("string");
+		writer.endObject();
+	}
 }

src/main/webapp/scripts/project/expression-preview-dialog.js

@@ -81,18 +81,32 @@ ExpressionPreviewDialog.prototype._renderHelpTab = function() {
 ExpressionPreviewDialog.prototype._renderHelp = function(data) {
     var elmt = this._elmts.helpTabBody.empty();
     
-    $('<h3></h3>').text("Functions").appendTo(elmt);
+    var renderEntry = function(table, name, entry) {
+        var tr0 = table.insertRow(table.rows.length);
+        var tr1 = table.insertRow(table.rows.length);
+        var tr2 = table.insertRow(table.rows.length);
         
-    var ul = $('<ul></ul>').appendTo(elmt);
-    for (var n in data.functions) {
-        $('<li></li>').text(n).appendTo(ul);
-    }
+        $(tr0.insertCell(0)).text(name);
+        $(tr0.insertCell(1)).text("(" + entry.params + ")");
+        
+        $(tr1.insertCell(0));
+        $(tr1.insertCell(1)).text("returns: " + entry.returns);
+        
+        $(tr2.insertCell(0));
+        $(tr2.insertCell(1)).text(entry.description);
+    };
+    
+    $('<h3></h3>').text("Functions").appendTo(elmt);
+    var functionTable = $('<table width="100%"></table>').appendTo(elmt)[0];
     
     $('<h3></h3>').text("Controls").appendTo(elmt);
+    var controlTable = $('<table width="100%"></table>').appendTo(elmt)[0];
     
-    ul = $('<ul></ul>').appendTo(elmt);
+    for (var n in data.functions) {
+        renderEntry(functionTable, n, data.functions[n]);
+    }
     for (var n in data.controls) {
-        $('<li></li>').text(n).appendTo(ul);
+        renderEntry(controlTable, n, data.controls[n]);
     }
 };