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7.5.19.0. AltVarStart
Procedure from library nctools.lib (see nctools_lib).

Usage:
AltVarStart();

Return:
int

Purpose:
returns the number of the first alternating variable of basering

Note:
basering should be a super-commutative algebra constructed by
the procedure superCommutative, emits an error otherwise

Example:
 
LIB "nctools.lib";
ring R = 0,(x(1..4)),dp; // global!
def ER = superCommutative(2); // (b = 2, e = N)
setring ER; ER;
==> // coefficients: QQ
==> // number of vars : 4
==> //        block   1 : ordering dp
==> //                  : names    x(1) x(2) x(3) x(4)
==> //        block   2 : ordering C
==> // noncommutative relations:
==> //    x(3)x(2)=-x(2)*x(3)
==> //    x(4)x(2)=-x(2)*x(4)
==> //    x(4)x(3)=-x(3)*x(4)
==> // quotient ring from ideal
==> _[1]=x(4)^2
==> _[2]=x(3)^2
==> _[3]=x(2)^2
"Alternating variables: [", AltVarStart(), ",", AltVarEnd(), "].";
==> Alternating variables: [ 2 , 4 ].
setring R;
"Alternating variables: [", AltVarStart(), ",", AltVarEnd(), "].";
==>    ? SCA rings are factors by (at least) squares!
==>    ? leaving nctools.lib::AltVarStart (1133)
kill R, ER;
//////////////////////////////////////////////////////////////////
ring R = 2,(x(1..4)),dp; // the same in char. = 2!
def ER = superCommutative(2); // (b = 2, e = N)
setring ER; ER;
==> // coefficients: ZZ/2
==> // number of vars : 4
==> //        block   1 : ordering dp
==> //                  : names    x(1) x(2) x(3) x(4)
==> //        block   2 : ordering C
==> // quotient ring from ideal
==> _[1]=x(4)^2
==> _[2]=x(3)^2
==> _[3]=x(2)^2
"Alternating variables: [", AltVarStart(), ",", AltVarEnd(), "].";
==> Alternating variables: [ 4 , 4 ].
setring R;
"Alternating variables: [", AltVarStart(), ",", AltVarEnd(), "].";
==>    ? SCA rings are factors by (at least) squares!
==>    ? leaving nctools.lib::AltVarStart (1133)