jv.thirdParty.expr

Class Parser

java.lang.Object

jv.thirdParty.expr.Parser

public class Parser
extends java.lang.Object

Parses strings representing mathematical formulas with variables. The following operators, in descending order of precedence, are defined:

• ^ (raise to a power such as 17^2 or sin(x)^2)
• * /
• Unary minus (-x)
• + -

Note: ^ associates right-to-left; other operators associate left-to-right.

These functions are defined: abs, acos(==arccos), asin(==arcsin), atan(==arctan), acot(==arccot), ceil, floor, exp, log(==ln), round, sign, sqrt, sin, cos, tan, cot, sinh, cosh, tanh, coth, asinh(==arcsinh), acosh(==arccosh), atanh(==arctanh), acoth(==arccoth). Lowercase and uppercase writing is ignored.

Each function requires one argument enclosed in parentheses. Whitespaces outside identifiers are ignored.

The syntax-error messages aren't very informative, unfortunately. IWBNI it indicated where in the input string the parse failed, but that'd be kind of a pain since our scanner is a StreamTokenizer. A hook for that info should've been built into StreamTokenizer.

Examples:

• 42
• 2-3
• cos(x^2) + sin(x^2)
• sqrt(y)^3

Author:

Darius Bacon

Version:

03.06.06 (kp) Alternative writings allowed such as log=ln, asin=arcsin.
06.08.99 (kp) StringBufferInputStream replaced with StringReader according to Java1.1.
07.07.99 (kp) New functions added: cot, acot, acosh, asinh, atanh, acoth, sign.
31.01.99 (kp) New functions added: cosh, sinh, tanh, coth.
00.00.96 (Darius Bacon) Original version.

Constructor Summary

Constructors

Constructor and Description
Parser()

Method Summary

Modifier and Type	Method and Description
static Expr	parse(java.lang.String input)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Parser

public Parser()

Method Detail

parse

public static Expr parse(java.lang.String input)
                  throws Syntax_error

Throws:

Syntax_error