Replace Pattern Matching

[liamblack]

I can't really tell does the program support Replace, ReplaceAll and ReplaceRepeated?

Basically does it support pattern matching?

[Axel Kramer]

The program should support ReplaceAll, ReplacePart and ReplaceRepeated.

For the missing Replace() function I started this commit: https://bitbucket.org/axelclk/symja_android_library/commits/566ac7b8caebe1d718490c787b0129534a1c7da4

at the moment the "level specification" feature isn't implmented for the Replace() function.

These are some examples which should work:

>>> {1 + a, 2 + a, -3 + a} /. (x_ /; x < 0) + a -> p(x)
{1+a,2+a,p(-3)}

>>> f(a) + f(b) /. f(x_) -> x^2
a^2+b^2

>>> u(v(w,x,y) /. { x->y, w->y})
u(v(y,y,y))

>>> u(v(w,x,y) /. x->y)
u(v(w,y,y))

[liamblack]

@axelclk I closed the issue as resolved, but how would do you examples in Java?

I believe this is a purely Java project yes?

[Axel Kramer]

There are methods in the IExpr interface: replaceAll(), replacePart, replaceRepeated()

public static void main(String[] args) {
        try {
            F.initSymbols(null, null, false);

            // expr = a+b+c
            IAST expr = F.Plus(F.a, F.b, F.c);
            // rule1 = b -> 10*d
            IAST rule1 = F.Rule(F.b, F.Times(F.integer(10), F.d));
            IExpr result = expr.replaceAll(rule1);
            if (result != null) {
                // print: a+10*d+c
                System.out.println(result.toString());
            }
            IAST listOfRules = F.List();
            listOfRules.add(rule1);
            // rule2 = b -> 10*e
            IAST rule2 = F.Rule(F.c, F.Times(F.integer(10), F.e));
            listOfRules.add(rule2);

            result = expr.replaceAll(listOfRules);
            if (result != null) {
                // print: a+10*d+10*e
                System.out.println(result.toString());
            }

        } catch (SyntaxError e) {
            // catch Symja parser errors here
            System.out.println(e.getMessage());
        } catch (MathException me) {
            // catch Symja math errors here
            System.out.println(me.getMessage());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

[Axel Kramer]

Added handling of "level specification" as 3rd argument in Replace() function:

https://bitbucket.org/axelclk/symja_android_library/commits/6cac457db85caa1b11235ca621d592709be0a152

[Axel Kramer]

a- b /. a -> x

is converted to

ReplaceAll( a- b , a -> x)

see:

FullForm(Hold(a- b /. a -> x))