Expression eval - Revision history

Theraze at 14:48, 16 December 2010

2010-12-16T14:48:46Z

← Older revision		Revision as of 14:48, 16 December 2010
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	}}\|		}}\|

	function_description= Evaluates an expression... ~~somehow~~.\|		function_description= Evaluates an expression using only the base components of the evaluator:

			* No spaces are allowed within the expression, except as part of a zone/location name.
			* + - * / ( ) have their usual mathematical meaning and precedence.
			* ^ is exponentiation, with the highest precedence.
			* Functions available: ceil(x) floor(x) sqrt(x) min(x,y) max(x,y)
			* Preferences function: pref(text)
			** This must be used on preferences with a float value ONLY - merely retrieving an integer pref will corrupt it!
			* There could be at most one of each text function in an expression.
			** This is no longer the case however and multiple of the same text functions should now work properly.
			* This wrapper allows user-defined variables to be used as well, which must have names starting with a lower-case letter (or underscore) to distinguish them from built-in variables. Variables are supplied as a float[string] map.
			\|

	code1={{CodeSample\|		code1={{CodeSample\|

Theraze at 14:39, 16 December 2010

2010-12-16T14:39:41Z

← Older revision		Revision as of 14:39, 16 December 2010
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	code1={{CodeSample\|		code1={{CodeSample\|
	title=Code Sample\|		title=Code Sample\|
	description=This script expands ~~modifier_eval~~() to include support for user-defined variables. It is extremely complex, but it is extremely useful to anyone who wants to use ~~modifier_eval~~().\|		description=This script expands expression_eval() to include support for user-defined variables. It is extremely complex, but it is extremely useful to anyone who wants to use expression_eval().\|
	code=		code=
	<syntaxhighlight>		<syntaxhighlight>
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	}		}
	m.append_tail(b);		m.append_tail(b);
	return ~~modifier_eval~~(b.to_string());		return expression_eval(b.to_string());
	}		}

Bale: Start page. This needs a lot of work. r8824

2010-12-16T10:37:04Z

Start page. This needs a lot of work. r8824

New page

{{
#vardefine:name|expression_eval}}{{
#vardefine:return_type|float}}{{

FunctionPage|
name={{#var:name}}|

function1={{Function|
name={{#var:name}}|
aggregate={{#var:aggregate}}|
return_type={{#var:return_type}}|
return_also={{#var:return_also}}|
parameter1={{Param|string|expression}}|
p1desc={{pspan|expression}} is a mathematical expression to be solved.|
}}|

function_description= Evaluates an expression... somehow.|

code1={{CodeSample|
title=Code Sample|
description=This script expands modifier_eval() to include support for user-defined variables. It is extremely complex, but it is extremely useful to anyone who wants to use modifier_eval().|
code=
<syntaxhighlight>
float eval(string expr, float[string] vars) {
buffer b;
matcher m = create_matcher( "\\b[a-z_][a-zA-Z0-9_]*\\b", expr );
while (m.find()) {
string var = m.group(0);
if (vars contains var) {
m.append_replacement(b, vars[var].to_string());
}
// could implement functions, pref access, etc. here
}
m.append_tail(b);
return modifier_eval(b.to_string());
}

# Everything below this line shows how to make use of eval().
# TESTING:

float[string] v;
v["pi"] = 3.14159265;
v["ten"] = 10;
print(eval("2+3", v));
print(eval("max(pi^ten,ten^pi)", v));
print(eval("sqrt(pi)*L", v));
print(eval("undefined/2", v));

</syntaxhighlight>}}|
}}

[[Category:Math and Numbers]]