subst() - substitute() 2.0☐ cool new feature
☐ could help many users!
☑ removes something that feels like a „bug“
☑ nice to have
☐ nobody needs it
What inspired this wish list request?
Substitute is a very powerful function for expression handling:
Using JSL to Develop Efficient, Robust Applications (EU 2018 415)
A big disadvantage of Substitute: it evaluates it's arguments : (
Therefore, Expressions with Substitute() get quite lengthy and hard to read. Besides that, a new JSL scripter has to learn the correct syntax - nobody expects that all those Expr() are necessary.
Example:
Substitute( Expr( a + Sqrt( a ) ), Expr( a ), Expr( b ) )
What is the improvement you would like to see?
A new function subst () which doesn't evaluate it's arguments. Then one can write :
Substitute( a + Sqrt( a ), a, b )
Why is this idea important?
Subst() and Eval(Subst()) will be used millions of times - and each time a JSL scripter will be happy that you implemented it!
other wishes from 
Automation and ScriptingRe: subst() - substitute() 2.0In most of the cases, the user will provide at least one of the arguments as a name - with the idea that JMP looks up the name and uses the Name Expr instead of the name itself.
So, JMP should evaluate the arguments to a level (look up, take the Name Expr if available, don't evaluate further) where it's possible to write:
a=Expr(myExpr);
Subst(x+y, x, a) // result: myExpr + y
</CODE>instead of </P><PRE><CODE class=" language-jsl">a=Expr(myExpr);
Substitute(Expr(x+y), Expr(x), Name Expr(a)) // result: myExpr + y
.
And if a user wants to be sure that JMP uses the argument as it is (without resolving the Name Expr.), he can write:
a=Expr(myExpr);
Subst(x+y, x, Expr(a)) // result: a + y
Re: subst() - substitute() 2.0With other words:
Subst()
... a Substitute() with the magic/easiness of Extract Expr()
clear symbols();
// direct mode, no Expr necessary
Extract Expr(x + y, x);// -> x
Extract Expr(x^2 + y, c);// no c in x^2 + y -> empty
// Name Expr mode
c=Expr(x^2);
Extract Expr(x^2 + y , c);// looks up c = x^2, find "x^2"" in x^2 +y
unfortunately, what doesn't work (as easy as I wished):
c=Expr(x^2);
Extract Expr(c * d, Expr(c))
Extract Expr
Re: subst() - substitute() 2.0 - Status changed to: AcknowledgedThank you for the suggestion @hogi .
