Support multi-line PARI formulas for multiple functions

CHANGELOG.md

@@ -3,7 +3,8 @@
 ### Enhancements
 
 * Support `fac` in LEAN formula generation
-* Improve LEAN formula generation for `pow`
+* Generalize LEAN formula generation for `pow`
+* Use multi-line output for PARI/GP formulas
 
 ## v25.11.2
 

src/form/pari.cpp

@@ -142,7 +142,16 @@ std::string PariFormula::toString() const {
     }
     return buf.str();
   } else {
-    return main_formula.toString("; ", true);
+    // Get all function definitions in the formula to determine output format
+    auto functions =
+        FormulaUtil::getDefinitions(main_formula, Expression::Type::FUNCTION);
+    if (functions.size() > 1) {
+      // Multiple functions: use newline separator and no brackets
+      return main_formula.toString("\n", false);
+    } else {
+      // Single function: use semicolon separator with brackets (original behavior)
+      return main_formula.toString("; ", true);
+    }
   }
 }
 

tests/formula/pari-function.txt

@@ -1,6 +1,8 @@
 A000023: a(n) = if(n==3,-2,if(n==2,2,if(n==1,-1,if(n==0,1,local(l1=a(n-1)); (n-1)*(2*a(n-2)+l1)-l1))))
 A000027: a(n) = n
 A000032: a(n) = if(n==2,3,if(n==1,1,if(n==0,2,a(n-1)+a(n-2))))
-A000058: (a(n) = b(n)+1); (b(n) = if(n==0,1,local(l1=b(n-1)); l1*(l1+1)))
+A000058: a(n) = b(n)+1
+  b(n) = if(n==0,1,local(l1=b(n-1)); l1*(l1+1))
 A000247: a(n) = 2^n-n-2
-A001715: (a(n) = truncate(b(n)/6)); (b(n) = if(n==0,1,n*b(n-1)))
+A001715: a(n) = truncate(b(n)/6)
+  b(n) = if(n==0,1,n*b(n-1))