# toExternalString(RationalMap) -- convert to a readable string

## Synopsis

• Function: toExternalString
• Usage:
toExternalString phi
• Inputs:
• phi,
• Outputs:
• , a string representation of phi, which can be used, in conjunction with value, to read the object back into the program later

## Description

All internal data of the input are included in the returned string.

 i1 : phi = (specialCubicTransformation(2,ZZ/33331))!; o1 : RationalMap (cubic birational map from PP^3 to hypersurface in PP^4) i2 : str = toExternalString phi; i3 : #str o3 = 7432 i4 : time phi' = value str; -- used 0.0133002 seconds o4 : RationalMap (cubic birational map from PP^3 to hypersurface in PP^4) i5 : time describe phi' -- used 0.00464406 seconds o5 = rational map defined by forms of degree 3 source variety: PP^3 target variety: smooth quadric hypersurface in PP^4 dominance: true birationality: true (the inverse map is already calculated) projective degrees: {1, 3, 4, 2} number of minimal representatives: 1 dimension base locus: 1 degree base locus: 5 coefficient ring: ZZ/33331 i6 : time describe inverse phi' -- used 0.0052128 seconds o6 = rational map defined by forms of degree 2 source variety: smooth quadric hypersurface in PP^4 target variety: PP^3 dominance: true birationality: true (the inverse map is already calculated) projective degrees: {2, 4, 3, 1} number of minimal representatives: 1 dimension base locus: 1 degree base locus: 5 coefficient ring: ZZ/33331