# Expression Help

## Contents

###

- Expression Syntax
- Order of Operators
- ExprEval Internal Functions
- ExprEval Internal Constants
- Application Internal Functions
- Application Internal Constants
- Application Internal Variables

## Expression Syntax

> Expressions have pretty much the same syntax as they would have on paper, with the following exceptions:

> - Each expression must end with a semicolon. This is because the expression string can actually contain multiple expressions. The semicolon is used to mark the end of the expression.
>   Examples:
>   - 4*x+5;
>   - y=5+2;g=4+6;
>   - y=r*sin(a);x=r*cos(a);
> - The asterisk '*' must be used to multiply.
>   Examples:
>   - y=5*6; Valid
>   - g=(x+1)*(x-1); Valid
>   - g=(x+1)(x-1); Invalid

> More than one expression may be contained within an expression string. As shown above, each expression must end with a semicolon, even if only one expression is in the string. The value of an expression string is the value of the last expression in the string.
> Examlples:

> - g=7; Value: 7
> - k=z+1; Value: z+1
> - r=4;k=6;o=9+r-k; Value: 9+r-k

> Some functions may take reference parameters. These parameters are references to other variables. You can mix reference parameters with normal parameters. The order of the normal parameters must remain the same and the order of the reference parameters must remain the same.
> Examples:

> - min(1,2,3,4,&mval); &mval is a reference to a variable mval
> - min(1,2,&mval,3,4); You may mix them inside like this.
> - min(1,2,(&mval),3,4); You may not nest reference parameters in any way

> Expressions may also be nested with parenthesis.
> Examples:

> - y=sin(x-cos(5+max(4,5,6*x)));
> - 6+(5-2*(x+y));

> Expressions may also have whitespace characters and comments. Whitespace characters such as newlines, linefeeds, carriage returns, spaces, and tabs are ignored. Comments begin with the pound sign '#' and end at the end of the line.
> Example:

>     #Set the x value
>     x = d * cos(r);

>     #Set the y value
>     y = d * sin(r);

> If a variable is used in an expression, but that variable does not exist, it is considered zero. If it does exist then its value is used instead.

> Notice: An expression can NOT assign to a constant and an expression can NOT use a constant as a reference parameter.

## Order of operators.

> The order of operators are processed correctly in ExprEval. The parameters to functions may be evaluated out of order, depending on the function itself.

> The following illustrates the order of operators:

> Operator | Direction | Example
> Functions and Parenthesis | N/A | (x + 5) * sin(d);
> Negation | Right to Left | y = -2;
> Exponents | Left to Right | y = x ^ 2;
> Multiplication and Division | Left to Right | x * 5 / y;
> Addition and Subtraction | Left to Right | 4 + 5 - 3;
> Assignment | Right to Left | x = y = z = 0;

## ExprEval Internal Functions

> The following functions are provided with ExprEval:

> Function | Min. Args | Max. Args | Min. Ref Args | Max. Ref Args | Result/Comment
> abs(v) | 1 | 1 | 0 | 0 | Absolute value of v. abs(-4.3) returns 4.3
> mod(v,d) | 2 | 2 | 0 | 0 | Remainder of v/d. mod(5.2,2.5) return 0.2
> ipart(v) | 1 | 1 | 0 | 0 | The integer part of v. ipart(3.2) returns 3
> fpart(v) | 1 | 1 | 0 | 0 | The fractional part of v. fpart(3.2) returns 0.2
> min(v,...) | 1 | None | 0 | 0 | The minimum number passed. min(3,2,-5,-2,7) returns -5
> max(v,...) | 1 | None | 0 | 0 | The maximum number passed. max(3,2,-5,-2,7) returns 7
> pow(a,b) | 2 | 2 | 0 | 0 | The value a raised to the power b. pow(3.2,1.7) returns 3.21.7
> sqrt(a) | 1 | 1 | 0 | 0 | The square root of a. sqrt(16) returns 4
> sin(a) | 1 | 1 | 0 | 0 | The sine of a radians. sin(1.5) returns around 0.997
> sinh(a) | 1 | 1 | 0 | 0 | The hyperbolic sine of a. sinh(1.5) returns around 2.129
> asin(a) | 1 | 1 | 0 | 0 | The arc-sine of a in radians. asin(0.5) returns around 0.524
> cos(a) | 1 | 1 | 0 | 0 | The cosine of a radians. cos(1.5) returns around 0.0707
> cosh(a) | 1 | 1 | 0 | 0 | The hyperbolic cosine of a. cosh(1.5) returns around 2.352
> acos(a) | 1 | 1 | 0 | 0 | The arc-cosine of a in radians. acos(0.5) returns around 1.047
> tan(a) | 1 | 1 | 0 | 0 | The tangent of a radians. tan(1.5) returns around 14.101
> tanh(a) | 1 | 1 | 0 | 0 | The hyperbolic tangent of a. tanh(1.5) returns around 0.905
> atan(a) | 1 | 1 | 0 | 0 | The arc-tangent of a in radians. atan(0.3) returns about 0.291
> atan2(y,x) | 2 | 2 | 0 | 0 | The arc-tangent of y/x, with quadrant correction. atan2(4,3) returns about 0.927
> log(a) | 1 | 1 | 0 | 0 | The base 10 logarithm of a. log(100) returns 2
> pow10(a) | 1 | 1 | 0 | 0 | 10 raised to the power of a. pow10(2) returns 100
> ln(a) | 1 | 1 | 0 | 0 | The base e logarithm of a. ln(2.8) returns around 1.030
> exp(a) | 1 | 1 | 0 | 0 | e raised to the power of a. exp(2) returns around 7.389
> logn(a,b) | 2 | 2 | 0 | 0 | The base b logarithm of a. logn(16,2) returns 4
> ceil(a) | 1 | 1 | 0 | 0 | Rounds a up to the nearest integer. ceil(3.2) returns 4
> floor(a) | 1 | 1 | 0 | 0 | Rounds a down to the nearest integer. floor(3.2) returns 3
> rand(&seed) | 0 | 0 | 1 | 1 | Returns a number between 0 up to but not including 1.
> random(a,b,&seed) | 2 | 2 | 1 | 1 | Returns a number between a up to and including b.
> randomize(&seed) | 0 | 0 | 1 | 1 | Seed the random number generator with a value based on the current time. Return value is unknown
> deg(a) | 1 | 1 | 0 | 0 | Returns a radians converted to degrees. deg(3.14) returns around 179.909
> rad(a) | 1 | 1 | 0 | 0 | Returns a degrees converted to radians. rad(180) returns around 3.142
> recttopolr(x,y) | 2 | 2 | 0 | 0 | Returns the polar radius of the rectangular co-ordinates. recttopolr(2,3) returns around 3.606
> recttopola(x,y) | 2 | 2 | 0 | 0 | Returns the polar angle (0...2PI) in radians of the rectangular co-ordinates. recttopola(2,3) returns around 0.588
> poltorectx(r,a) | 2 | 2 | 0 | 0 | Returns the x rectangular co-ordinate of the polar co-ordinates. poltorectx(3,1.5) returns around 0.212
> poltorecty(r,a) | 2 | 2 | 0 | 0 | Returns the y rectangular co-ordinate of the polar co-ordinates. poltorecty(3,1.5) returns around 2.992
> if(c,t,f) | 3 | 3 | 0 | 0 | Evaluates and returns t if c is not 0.0. Else evaluates and returns f. if(0.1,2.1,3.9) returns 2.1
> select(c,n,z[,p]) | 3 | 4 | 0 | 0 | Returns n if c is less than 0.0. Returns z if c is 0.0. If c is greater than 0.0 and only three arguments were passed, returns z. If c is greater than 0.0 and four arguments were passed, return p. select(3,1,4,5) returns 5
> equal(a,b) | 2 | 2 | 0 | 0 | Returns 1.0 if a is equal to b. Else returns 0.0 equal(3,2) returns 0.0
> above(a,b) | 2 | 2 | 0 | 0 | Returns 1.0 if a is above b. Else returns 0.0 above(3,2) returns 1.0
> below(a,b) | 2 | 2 | 0 | 0 | Returns 1.0 if a is below b. Else returns 0.0 below(3,2) returns 0.0
> avg(a,...) | 1 | None | 0 | 0 | Returns the average of the values passed. avg(3,3,6) returns 4
> clip(v,min,max) | 3 | 3 | 0 | 0 | Clips v to the range from min to max. If v is less than min, it returns min. If v is greater than max it returns max. Otherwise it returns v. clip(3,1,2) returns 2
> clamp(v,min,max) | 3 | 3 | 0 | 0 | Clamps v to the range from min to max, looping if needed. clamp(8.2,1.3,4.7) returns 1.4
> pntchange(side1old, side2old, side1new, side2new, oldpnt) | 5 | 5 | 0 | 0 | This is used to translate points from different scale. It works no matter the orientation as long as the sides are lined up correctly. pntchange(-1,1,0,480,-0.5) returns 120 (x example) pntchange(-1,1,480,0,-0.5) returns 360 (y example)
> poly(x,c1,...) | 2 | None | 0 | 0 | This function calculates the polynomial. x is the value to use in the polynomial. c1 and on are the coefficients. poly(4,6,9,3,1,4) returns 2168 same as 6*44 + 9*43 + 3*42 + 1*41 + 4*40
> and(a,b) | 2 | 2 | 0 | 0 | Returns 0.0 if either a or b are 0.0 Else returns 1.0 and(2.1,0.0) returns 0.0
> or(a,b) | 2 | 2 | 0 | 0 | Returns 0.0 if both a and b are 0.0 Else returns 1.0 or(2.1,0.0) returns 1.0
> not(a) | 1 | 1 | 0 | 0 | Returns 1.0 if a is 0.0 Else returns 0.0 not(0.3) returns 0.0
> for(init,test,inc,a1,...) | 4 | None | 0 | 0 | This function acts like a for loop in C. First init is evaluated. Then test is evaluated. As long as the test is not 0.0, the action statements (a1 to an) are evaluated, the inc statement is evaluated, and the test is evaluated again. The result is the result of the final action statement. for(x=0,below(x,11),x=x+1,y=y+x) returns 55.0 (if y was initially 0.0)
> many(expr,...) | 1 | None | 0 | 0 | This function treats many subexpressions as a single object (function). It is mainly for the 'for' function. for(many(j=5,k=1),above(j*k,0.001),many(j=j+5,k=k/2),0)

## ExprEval Internal Constants

> The following constants are provided with ExprEval:

> Constant | Math Form | Value
> M_E | e | 2.7182818284590452354
> M_LOG2E | log2(e) | 1.4426950408889634074
> M_LOG10E | log10(e) | 0.43429448190325182765
> M_LN2 | ln(2) | 0.69314718055994530942
> M_LN10 | ln(10) | 2.30258509299404568402
> M_PI | π | 3.14159265358979323846
> M_PI_2 | π/2 | 1.57079632679489661923
> M_PI_4 | π/4 | 0.78539816339744830962
> M_1_PI | 1/π | 0.31830988618379067154
> M_2_PI | 2/π | 0.63661977236758134308
> M_1_SQRTPI | 1/√(π) | 0.56418958354776
> M_2_SQRTPI | 2/√(π) | 1.12837916709551257390
> M_SQRT2 | √(2) | 1.41421356237309504880
> M_1_SQRT2 | 1/√(2) | 0.70710678118654752440

## Application Internal Functions

> Application defined expression functions go here.

> Function | Min. Args | Max. Args | Min. Ref Args | Max. Ref Args | Result/Comment

## Application Internal Constants

> Application defined expression constants go here.

> Constant | Math Form | Value

## Application Internal Variables

> Application defined expression variables go here.

> Variable | Math Form | Value