使用purrr更改Post请求中的正文值

Question

我正在尝试使用httr和purrr执行多个POST请求。每个POST请求都必须更改页面参数。有了for循环，我会这样做：

library(httr)
library(xml2)
library(stringr)

url<-"http://busca.tjsc.jus.br/jurisprudencia/buscaForm.do"

a<-GET(url)

body<-list(q = "", only_ementa = "", frase = "", excluir = "", 
             qualquer = "", `NA` = NA_character_, prox1 = "", prox2 = "", 
             proxc = "", sort = "dtJulgamento desc", ps = "50", busca = "avancada", 
             pg = "1", flapto = "1", radio_campo = "integra", `categoria[]` = "acordaos", 
             faceta = "false")

body[[1]]<-"indulto"

  url2<-"http://busca.tjsc.jus.br/jurisprudencia/buscaajax.do?&categoria=acordaos"

  b<-POST(url2,body=body,encode="form",set_cookies(unlist(a$cookies)))

pages<- b %>% 
    httr::content() %>% 
    xml_find_all("//*[@class='texto_resultados']") %>%
    xml_text() %>% 
    str_extract("\\d+") %>% 
    as.numeric() %>% 
    `/`(50) %>% 
    ceiling()

c<-NULL
for(i in 1:pages){
    body[[13]]<-i
    d<-url2 %>% POST(body=body,encode="form",set_cookies(unlist(a$cookies))) %>% 
      httr::content() %>% 
      xml_find_all("//*[@id='coluna_principal']/div/div[3]/a/@href") %>% 
      xml_text() %>% 
      paste0("http://busca.tjsc.jus.br/jurisprudencia/",.)
    c<-c(c,d)
  }

有人可以帮我解决如何使用purrr :: map吗？