### 2.21.23  Rewrite an expression with different options : convert convertir

convert takes two arguments an expression and an option.
convert rewrites this expression applying rules depending on the option. Valid options are :

• sin converts an expression like trigsin.
• cos converts an expression liketrigcos.
• sincos converts an expression like sincos.
• trig converts an expression like sincos.
• tan converts an expression like halftan.
• exp converts an expression like trig2exp.
• ln converts an expression like trig2exp.
• expln converts an expression like trig2exp.
• string converts an expression into a string.
• matrix converts a list of lists into a matrix.
• polynom converts a Taylor series into a un polynomial by removing the remainder (cf 2.24.22).
• parfrac or partfrac or fullparfrac converts a rational fraction into it’s partial fraction decomposition (2.28.9).

convert can also :

• convert units, for example convert(1000_g,_kg)=1.0_kg (cf 5.1.4).
• write a real as a continued fraction : convert(a,confrac,’fc’) writes a as a continued fraction stored in fc. Do not forget to quote the last argument if it was assigned.
For example, convert(1.2,confrac,’fc’)=[1,5] and fc contains the continue fraction équal to 1.2 (cf 2.8.7).
• transform an integer into the list of its ciphers in a basis, begining with the unit cipher (and reciprocally)
• convert(n,base,b) transforms the integer n into the list of its ciphers in a basis b begining with the unit cipher.
For example, convert(123,base,10)=[3,2,1] and reciproqualy
• convert(l,base,b) transforms the list l into the integer n which have l as list of its ciphers in a basis b begining with the unit cipher.
For example, convert([3,2,1],base,10)=123 (cf 2.5).